codec: calculate theoretical minimal overhead

codec: calculate theoretical minimal overhead

Optimal sizes of 1x1 black images as researched by Jon Sneyers [1]
with later AVIF data [2] and 2021-10-25 breakthrough for JPEG-XL [3].

An example found for HEIC [4] may not be golfed, but kind of irrelevant
considering the container.  Its 212 byte JPEG-2000 example is larger than a
naive ImageMagick conversion.

[1] https://cloudinary.com/blog/one_pixel_is_worth_three_thousand_words
[2] https://twitter.com/jonsneyers/status/1333037638840967169
[3] https://twitter.com/jonsneyers/status/1452727349405966341
[4] https://github.com/mathiasbynens/small/commit/e05a006dd